Alzheimer's disease (AD) is a neurodegenerative disorder of advanced age characterized by loss of memory, accumulation of amyloid beta protein (Aβ) deposits and decreased levels of the neurotransmitter acetylcholine. Approximately forty percent of AD patients suffer from significant depression. 5-HT4 receptor partial agonists may be of benefit for both the symptomatic and disease-modifying treatment for AD and may offer improved clinical efficacy and/or tolerability relative to acetylcholine esterase inhibitors. 5-HT4 receptor agonists also have antidepressant like properties (Expert Review of Neurotherapeutics, 2007, 7, 1357-1374; Experimental Neurology, 2007, 203(1), 274-278; Neuroscience & Medicine, 2011, 2, 87-92; Schizophrenia Bulletin, 2007, 33 (5), 1100-1119).
1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I) is a promising pharmaceutical agent, which is a potent, selective and orally bioavailable 5-HT4 receptor partial agonist intended for both disease modifying and symptomatic treatment of Alzheimer's disease and other disorders of memory and cognition like Attention deficient hyperactivity, Parkinson's and Schizophrenia. In addition to the pro-cognitive effects, the compound also demonstrated dose dependent antidepressant like effects in the mouse forced swim test. 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate and its synthesis is disclosed by Ramakrishna et al. in WO2013042135.
At present, 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I) has completed preclinical studies and is ready to enter human clinical trials. The demand for 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I) as a drug substance would be increased substantially with the advent of its human clinical trials. The future need for much larger amounts is projected due to the intended commercialization of 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I).
For the person skilled in art, it is a well known fact that various parameters will change during the manufacturing of a compound on a large scale when compared to the synthetic procedures followed in laboratory. Therefore, there is a need to establish and optimize large scale manufacturing process. The process for the preparation of 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I) which was disclosed in WO2013042135 had been proved to be unsatisfactory for the large scale synthesis. Eventually, it is highly desirable to establish optimized manufacturing process for 1-Isopropyl-3-{5-[1-(3-methoxypropyl) piperidin-4-yl]-[1,3,4]oxadiazol-2-yl}-1H-indazole oxalate of formula (I) which is amenable to the large scale preparation.